1. Field of the Invention
This invention relates to a supercharging device for internal combustion engines which incorporates a turbo-compressor driven by the engine exhaust gases.
2. Description of the Prior Art
It is known that when a turbo-compressor or turbo-charger is used a back-pressure develops in the engine exhaust system. A far from negligible consequence of this back-pressure is a substantial increase in the fuel consumption. Thus, by eliminating or at least minimizing this back-pressure it is possible to reduce the fuel consumption, in certain cases by as much as ten percent. It is also known that the primary object of the present use of an exhaust gas by-pass, usually referred to as a "waste-gate", actuated by a control valve responsive to the supercharger output pressure, is to limit the intake supercharging pressure to a predetermined threshold, for the obvious purpose of protecting the engine.
More particularly, the present invention is based on the advantage derived from controlling the opening and closing of the above-defined exhaust-gas waste-gate as a function of engine power demands. In fact, at low r.p.m. values and under part-load engine operation a certain degree of supercharging is necessary and consequently the waste-gate can be opened to reduce the exhaust back-pressure and therefore improve the fuel consumption. At higher engine speeds said waste-gate can be gradually closed according to power requirements. In this mode of operation, the exhaust back-pressure is lower than in the conventional use of the waste-gate, the latter opening only at one engine protection value, and nevertheless a fuel consumption gain will still result.